The engines to which the invention relates may be spark-ignition engines or compression-ignition (diesel) engines. The engines may be supercharged or aspirated.
A motor vehicle internal combustion engine includes a combustion chamber, generally formed by a plurality of cylinders, in which a mixture of fuel and oxidant is burned to generate the work of the engine. The gases admitted into the combustion chamber are called inlet gases. They include air called charge air when it comes from a compressor.
In order to increase the density of the charge air, these gases are generally cooled before being introduced into the combustion chamber. This is done by a heat exchanger also known as a charge air cooler (CAC).
To reduce polluting emissions it is known to introduce so-called “recirculated” exhaust gases into the inlet gas flow, a process known to the person skilled in the art as exhaust gas recirculation (EGR). These are exhaust gases bled off on the downstream side of the combustion chamber to be rerouted (recirculated) to the inlet gas flow, on the upstream side of the combustion chamber, where they are mixed with the charge air for their admission into the combustion chamber.
In order to admit into the engine block of a motor vehicle internal combustion engine a charge air flow including an inlet gas flow, that is to say a cool air flow, and/or a recirculated exhaust gas flow, an inlet manifold intended to be mounted on the engine block enables optional mixing of the cool air flow and the recirculated exhaust gas flow and distribution of the mixture into the engine block.
In this case, means are provided for routing recirculated exhaust gases into the inlet manifold enabling the distributed injection of the recirculated exhaust gases into the charge air flow.
In accordance with one known solution, the recirculated exhaust gases (EGR gases) are introduced into the inlet manifold via a distribution duct arranged transversely to the charge air flow, discharging for example on the downstream side of the charge air cooler and including a few injection holes that enable the recirculated exhaust gas to flow into the volume of the inlet manifold.
The recirculated exhaust gases are able to mix with the inlet gases coming for example from the charge air cooler. The mixture is then directed toward the outlet ducts to feed the cylinder(s) of the engine.
However, the size and the position of the injection holes are fixed. In fact, the size and the disposition of the holes are predefined for a certain range of operation of the engine and cannot be modified while the engine is operating.
By way of example, injection holes having a certain diameter enable a satisfactory exhaust gas level to be obtained in the cylinders for an engine speed of around 1 250 rpm. However, with this same diameter the recirculated exhaust gas level in the cylinders is not satisfactory for an engine speed around 2 000 rpm. The converse is equally valid.
In conclusion, it is necessary to choose a size that is suitable for one engine speed range but not for the others. This leads to an optimum distribution limited to a narrow range of operation of the engine.